Inorganic nanomaterials offer immense potential in therapeutic and diagnostic (theranostic) applications. One major concern that limits the clinical translation of inorganic nanomaterials is toxicity resulted from long-term retention or toxic degradation by-products. Therefore, biodegradation into non-toxic components is an ideal property for materials aimed at theranostic applications. Phosphate-based bulk glasses have been found biocompatible and biodegradable. However, the theranostic application of phosphate glasses is still limited by the lack of a simple synthetic approach for preparing phosphate nano-/microparticles with controllable sizes. Inspired by the bio-silicification process found in diatom, we designed a PEI-mediated sol-gel strategy for this purpose. This method is simple and mild and can prepare PEI/calcium phosphate (PEI/CP) micro-/nanostructures in the range of 63 µm to 400 nm with interesting morphologies and shapes (e.g. hexagonal micro-plate, micro-flower, micro-leaf, nano-sphere, nano-butterfly and nano-ribbon). PEI/CPs can degrade in aqueous solutions within 24 hours, as demonstrated by ICP-MS and optical microscope. Besides, low cell cytotoxicity was found using HEK293T and Hela cell lines. In vitro B-mode and Doppler ultrasound imaging tests showed that PEI/CPs can generate intense ultrasound signals and these signals decreased within 24 hours as they biodegraded. All of these findings suggest that PEI/CPs may be applied for transient ultrasound imaging. Future work will apply this synthetic strategy for doping various elements (e.g. Si, Mg, Na, K) into these micro-/nanostructures to further control the degradation rate, which may open up opportunities for more theranostic applications.

Biomimetic synthesis of versatile biodegradable polyethylenimine/calcium phosphate micro-/nanostructures for transient ultrasound imaging

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.